This invention relates to a mobile communication system and, more particularly, to a cellular communication system for providing communication with mobile stations.
A cellular communication system is popular in the mobile communication. The cellular communication network is shared between many subscribers. However, the subscribers are usually getting more and more. For this reason, a district covered with the cellular communication network is divided into wide service areas at the initial stage of the business, and the wide service area is further divided into narrow service areas together with the development of the business. Thus, the subscribers in each service area do not exceed a certain limit, and the cellular communication network is prevented from serious congestion. Even if the serious congestion takes place in a narrow service area, the serious congestion does not affect the communication in the other narrow service areas, and the cellular communication system permits most of the subscribers to communicate with one another.
However, the prior art cellular communication system requires base stations in the narrow service areas, respectively, and the base stations independently behave in the individual narrow service areas. This means that the prior art cellular communication network can not interchange the communication channels between the congestion area and the non-congestion area. This is the first problem inherent in the prior art cellular communication network.
Another problem is high construction cost. When the subscribers in a service area exceeds the limit, the service area is divided into plural narrow areas, and a new base stations is to be constructed in the narrow area. Even though other service areas do not exceed the limit, the new base station is required for the narrow area. The new base station is expensive, and pushes up the construction cost of the prior art cellular communication network.
Yet another problem relates to the division of a service area into narrow areas. The new base stations are to be located at appropriate places in the associated narrow service areas from the viewpoint of propagation of electro-magnetic waves. However, the most appropriate place is not always vacant. This means a difficult negotiation with the owner. Thus, the third problem is the difficulty in the favorable location of the new base station.
It is therefore an important object of the present invention to provide a cellular communication system, which is flexible and low in construction cost without influence of local congestion.
In accordance with one aspect of the present invention, there is provided a cellular communication system for a real space divided into plural service areas, at least one of the plural service areas contains a first service sub-area, and the cellular communication system comprises plural base stations respectively installed in the plural service areas and creating communication channels in the associated service areas, respectively, plural mobile stations each movable in the real space and selectively communicating with the plural base stations through the communication channels, an exchange and control station connected to the plural base stations through communication lines, connecting at least the mobile stations through the communication channels, the plural base stations and the communication lines to one another and supplying a piece of system information indicative of a special service requested in the first service sub-area and different from a standard communication service between at least the mobile stations to the base station in the aforesaid at least one of the plural service areas and a set of communication facilities installed in the first service sub-area and creating an information channel to the mobile stations in the first service sub-area for transferring the piece of system information, thereby realizing the special service in the first service sub-area.